Process of producing potassium sulphate, ammonia sulphate, and alumina from alunite



Patented Mar. 15, 1932 UNETE QSTATESY HIROM'U TANAKA, or SUGINAMI-MACHI, ToYoTAM-meUn,.a oicYo; TJA'BAN '5:

assumes PROCESS or PRODUCING POTASSIUM soLrna'rnjalvriu'o iira spLPHaTnlrn-D, ALUMINA FROM annu ar. H

N Drawing. Application filed January 2, 1929, Serial 395,950, "madam ata ra a a,

This invention relates to'the process of producing potassium sulphate, ammonium sulphate and alumina from alunite, characterized in that alunite, after being calcined, is subjected to the action of ammonia which will produce ammonium sulphate; the said sulphate together with potassium sulphate, is lixiviated, its residue being treated with sulphurous acid at the heat of 60 to- 70 degrees C., and the resulting aluminum sulphite solution is then subjected to the heat of about 100 degrees 6., aluminum being precipitated as a basic sulphite which is converted to alumina by calcination. Thus,

I this invention has, for its object, the utilization of every component of alunite in the most effective and useful manner.

completed the process of utilizing any and all of alumina, potash, and sulphur trioxide contained in alunite which will be demonstrated in the following paragraphs. WVhen alunite is heated at about 600 C. and

* treated with ammonia, decomposition sets in as shown in the equation which is and the potassium sulphate is separated from alumina together with the ammonium sulphate in the form of solution. Then as the next process, the residual alumina is treated with sulphurous acid when it readily dissolves and separates from silica resulting in aluminum sulphite solution, which when heated at about 100 0., liberates a greater part of S0 and the basic aluminum sulphite Al O .3SO is thrown down. Lastly, pure alumina is obtained by heating the said precipitate at over 900 C.

Following is an example of working this invention.

Alunite is first powdered, and after being in a furnace at about 600 C., is placed in a covered vessel; The theoretical amount ammonia 1 moderately concentrated is added to the calcined alums and agitation is conail-tea for about one hour, then reaction heat is generatedto alarge extent resulting in "ammonium" sulphate caused by the reaction "of ammonia. on'the alunit'e, which ent'ersinto solution together with'potassium sulphate to the extent of more than percent of the originally contained amount, The insoluble 7 residuebeing separated by 'mea'ns of filter press orvacuumlfi-l ter, thefiltrate is evaporatedand'ismade to crystallize into aEmiX- ture of am inonium' and potassium sulphates which is to be used as a mixed fertilizer of potash and nitrogen; The insoluble residue above-mentioned which is. an ammina con} taining silica anda smallquantityof iron oxide, is "transferred "into an airetight; and l'ea'c l-linedfdigester and after .adding water to times the weight of alumin'aji'oon .ta inedj in the residue, is treatedunder ordinary or a; few "atmospheres pressure and at to 'degreesfC. for toi5 hours, intro- 'clucing, i11to the solution, sulphur dioxide which is liberated 'di ring the decomposition of aluminum sulphite; By this treatment more than per cent of alumina dissolves into sulphite solution. The solution is then clarified by filtration or decantatiomf and taken into a decomposer of a similar construction with the digester above-mentioned. Steam is then passed to a steam jacket or coil and temperature of the decomposer is kept at about 100 C. which liberates a greater part of SO in the solution, and aluminum is completely precipitated in the form of free from iron and easily filterable. Then the precipitate is passed into an air-tight filter such as filter press, washed and is lastly calcined, after being dried, at the heat over 900 C. when it is converted into pure alumina, liberating'all of the combined sulphur dioxide and Water. It is to be added that SO gas emitting from the decomposer and calciner is to be recovered and is utilized for the process cyclically.

As described in the foregoing paragraphs,

the process invented will enable all the alumina, potash and sulphur trioxide contained in alunite, to be utilized each as a valuable product. 7 Claims: i

1. The process of manufacturing alumina,

potassium sulphate and ammonium sulphate from alunite, which comprises calcining alunite at a temperature of approximately 10 600 (3., reacting ammoniaiwater with the calcined alunite to form potassium and ammonium sul hates and alumina containing impurities, ltering the solution to remove the aluminous residue, and then'treating the t aluminous residue with sulphurous acid for dissolving the .alumina, boiling the solution thus obtained to causeprecipitation of alumina as a basic sulphite and calcining the precipitate whereby pure alumina is obtained.

' 29 2. The processof manufacturing alumina,

' potassium sulphate and ammonium sulphate from alunite which comprises calcining the alunite at approximately 600 (1, then reacting ammonia Water with the calcined 5 alunite while agitating the same to form potassium sulphate, ammonium' sulphate and an insoluble residue containing alumina, removing the residue and adding water thereto, passing sulphur dioxide through the mix- 30 ture of the residue and water at 6070 C. at approximately atmospheric pressure for dissolving alumina and forming a sulphite solution of aluminum,rfiltering the solution and heatingthe same for liberating a greater portion of the sulphur dioxide, while precipitating a basic sulphite of aluminum, and calcining'the precipitate at about 900 0.,

thereby liberating the sulphur dioxide with the consequent residueof pure alumina. 40 In testimony whereof I have signed my name to this specification.

HIROMU 'TANAKA. 

